Nettie Stevens

Nettie Maria Stevens (7 July 1861-4 May 1912) was an American geneticist who discovered sex chromosomes and named them "X" and "Y" chromosomes.

Biography
Nettie Maria Stevens was born in Cavendish, Vermont in 1861, and the family moved to Westford, Massachusetts in 1863. She and her sister were 2 of the 3 women who graduated from Westford Academy between 1872 and 1883, graduating in 1880. In 1896, she enrolled at the newly established Stanford University, and her PhD advisor was Thomas Hunt Morgan, who later convinced her to attend Columbia University. In 1905, soon after the rediscovery of Gregor Mendel's 1900 paper on genetics, she discovered that male mealworms produced two kinds of sperm, one with a large chromosome and one with a small chromosome. When the large chromosomes fertilized eggs, they became females, and the small ones produced males; Stevens and Edmund Beecher Wilson would independently discover sex chromosomes, which Stevens called "X" and "Y". Stevens died in Baltimore, Maryland in 1912 at the age of 50, publishing 40 papers during the brief nine years' time between her PhD and her passing.